The present invention relates to the preparation of 5-(4-aminobutyl) hydantoin and/or 2-ureido-6-aminocapronamide by hydrogenating 5-(3-cyanopropyl) hydantoin and/or 2-ureido-5-cyano-valeramide in the liquid phase and in the presence of ammonia using a hydrogenation catalyst. The reaction product can be converted into lysine by hydrolysis according to known procedures.
This type of hydrogenation can be carried out with various hydrogenation catalysts, and gives high yields according to U.S. Pat. Nos. 3,758,494 and 3,911,001. In most cases according to these patents, nickel or cobalt is preferred as hydrogenation catalyst.
However, a closer study of this hydrogenation process has revealed that with nickel, cobalt or both being used as the catalyst, fairly large amounts of catalyst are lost owing to dissolution of the nickel or cobalt in the reaction medium.